Atomistic study of fracture of nanoscale materials by molecular dynamics and lattice Green's function methods

Abstract
The fracture behaviors of nanoscale sp-bonded materials have been studied using the molecular dynamics and lattice Green's function methods. The initial atomic structures of the crack are determined both from the elastic solutions as well as from those by lattice Green's function method for the infinite systems. Firstly, we calculate the Green function for the defective lattice, with dislocation and crack, by solving the Dyson equation, appropriate for absolute zero temperature. After the lattice Green functions of the absolute zero temperature have been determined, the lattice parameters and interatomic force constants are adjusted to fit to materials at temperature T. In general, we have found that the lattice trapping and stress intensity factors for dislocation emission KIle. The fracture and strength properties are also investigated for the nanocrystalline materials like semiconductor quantum wire and nanotubes. The O(N) tight-binding molecular dynamics (TBMD) method is used to analyze the reconstruction of atomic bonding near the crack tip as well as the cleaved surface. We compare the fracture behavior of nanoscale materials with those of corresponding bulk-size materials.